1. Field of the Invention
This invention relates to methods for fabricating deep diode, or semiconductor, atomic batteries.
2. Description of the Prior Art
Batteries were the first source of harnassed electric energy used by man and are still one of the most practiced sources of portable electric energy. Most batteries operate on the general principle of converting chemical energy directly into electric energy. As a result of this dependence on chemical reactors, the performance of most batteries can be affected adversely by temperature and pressure changes. In addition, the shelf life of such chemical batteries is relatively limited. Moreover, as a result of the build-up of chemical reaction products from the chemical reactions being utilized to produce electric current, the internal resistance of a chemical battery increases with use so that an increasing share of the electrical energy is dissipated as wasted energy in the battery itself rather than as useful energy in an external load. Another limitation of chemical batteries is the storage capacity of such batteries in terms of available electric energy per unit volume or per unit weight of a battery. For example, electric-powered vehicles have been generally impractical because of this factor. Many chemical batteries must be discarded after use. Those that can be recharged require inconveniently long charging times and can only be subjected to a limited number of charging and discharging cycles. Chemical batteries can be irreparably damaged by accidental short circuiting resulting from failures in the load circuit or structural failures in the battery itself from vibrations or severe accelerational forces.
In the 1950's, a beta-ray radiosotropic battery was developed which was superior in a number of characteristics to the conventional chemical battery. Beta rays consist of a stream of high energy electrons. A beta-ray radio isotope battery can be constructed by using an emitter anode coated with a radio isotope that emits beta-rays (electrons) to a collector cathode that collects the electrons emitted from the radioactive anode. The emitter anode becomes positively charged as beta-rays (electrons with negative charges) leave it and the collector cathode becomes negatively charged as it absorbs these high energy electrons. Because the beta-rays have considerable energy and thus are able to overcome moderate electric field forces, such cells are capable of producing a high voltage if enough time elapses for charges to build up. With a large capacitor in parallel with the beta-ray radioisotope battery, enough charge can be accumulated to give output currents of 40 amps at zero voltage and lower currents at maximum voltages of 6,000 volts after two months.
Other means of transforming the energy emitted in radioactive decay into electrical energy have been developed in recent years. Flourescence/Photoelectric batteries achieve an indirect nuclear to electrical energy conversion by using radiation to excite fluorescent material and using the generated light to operate a photoelectric cell. The overall efficiency of this battery is very low because it utilizes two low efficiency processes.
Thermoelectric type batteries use the heat output from a highly radioactive source and the thermoelectric effect to generate electricity. These cells are generally designed to use radioactive sources of thousands of curies. Because of the low penetration ability of alpha particles, alpha particle emitters are used in these cells so that low radioactivity levels outside of the cell are obtainable without excess shielding.
Gas ionization batteries have also been developed using particles emitted from a radioactive source to generate numerous ion pairs in the gas, the "electrolyte" of the battery. The anode and the cathode are metals that have a large contact potential difference between them so that an electric field exists between the anode and thode. This field separates the positive and negative ions and causes them to drift to opposite electrodes where they are discharged and cause a current in the external circuit of the battery. The output of this type of cell gives about one-half volt and several microamps.
Thermionic batteries have been constructed using the heat output from a radioactive source to liberate electrons from an anode with a low work function and to collect these same thermal electrons on a cold cathode. Efficiencies of up to 15 percent are possible with this type of battery.
P-N junction barriers have been made by irradiating a P-N junction with Beta particles. The electron-hole pairs formed by the absorption of the high energy beta particles are separated by the built in field of the P-N junction and thereby produce a current. Relatively high efficiencies are possible because each high energy beta particle produces many electron-hole pairs.
Finally, Compton scattering batteries have been made which employ gamma rays from a gamma emitter. In this battery the anode and the cathode are separated by an insulating material. Gamma rays emitted from a radioactive source separated from the anode knock electrons out of the insulator material with a preferential forward direction onto the anode where they are collected. The efficiency of this battery is very low.
An object of this invention is to provide a new and improved method for fabricating a deep diode atomic battery which overcomes the deficiencies of the prior art.
An object of this invention is to provide a new and improved method for fabricating a deep diode atomic battery embodying thermal gradient zone melting to fabricate the structure of the battery.
Another object of this invention is to provide a new and improved method for providing an integral source of energy for powering a deep diode atomic battery.
Other objects of this invention will, in part, be obvious and will, in part, appear hereinafter.